1. Field of the Invention
The present invention relates to a zoom camera, and more particularly, to a barrel assembly of a zoom camera having a linear trace of zoom.
2. Description of the Related Art
A zoom lens in a camera is used to take photographs by changing a focal distance within a particular range to change the magnification ratio of an image. Also, the zoom lens refers a lens structure enabling variable-focal length.
The zoom lens includes a front lens group mainly having positive power and a rear lens group mainly having negative power. By relatively moving the lens groups, the distance between the lens groups and the distance between the lens groups and the surface of a film fixed to a body of a camera are adjusted so that zoom is performed.
A conventional zoom lens includes two screw shafts for moving lens groups and a power switching mechanism. According to the structure of the zoom lens, each of the lens groups is moved by rotation of the respective screw shafts to perform zoom. When the zoom operation is completed, only one screw is driven by the power switching mechanism to move a lens to complete focusing. However, in the above zoom lens structure, the distance that a zoom lens moves increases to obtain a high power and the structure of the power switch mechanism is complicated. Accordingly, since a space for installation of the zoom lens is needed, it is difficult to make a camera to be compact.
In another structure of a zoom lens, a cam barrel is coupled to a fixed barrel which is fixed to a body of a camera. A front lens group moves linearly with respect to the cam barrel and the rear lens group moves non-linearly while rotating along a cam groove formed on an inner circumferential surface of the cam barrel. Accordingly, the front group lens moves linearly while the rear group lens moves non-linearly, thus performing a zoom operation.
In this case, focusing is performed as the front group lens is moved by a motor installed at a shutter block. However, the processing of the cam barrel is difficult and the structure of a barrel assembly of a zoom camera is complicated. Thus, a zoom lens which enables a camera to have a high power and in a compact size and in which a point where a cam curve changes is not generated when the lens groups move, is requested.
To solve the above problems, it is an objective of the present invention to provide a barrel assembly of a zoom camera which prevents an unsmooth zoom operation due to overload of a cam when the zoom operation is performed at the curve changing point as the front and rear lens groups are linearly moved, and which can reduce defectiveness in the zoom operation generated due to a process error and an assembly error.
Accordingly, to achieve the above objective, there is provided a barrel assembly of a zoom camera comprising a zoom ring at which a front lens group is installed and which is moved back and forth along the optical axis, a rear lens group frame at which a rear lens group is installed along the same optical axis as the front lens group and which is coupled to the zoom ring, and a cam means for correcting the optical position of the rear lens group with respect to the front lens group during operation of zoom.
Also, to achieve the above objective, there is provided a barrel assembly of a zoom camera comprising a zoom ring at which a front lens group is installed and which is moved back and forth along the optical axis, a rear lens group frame at which a rear lens group is installed along the same optical axis as the front lens group and which is coupled to the zoom ring, a cam means for correcting the optical position of the rear lens group with respect to the front lens group during operation of zoom, the cam means comprising an inner rotator rotatably coupled to the zoom ring and a cam protrusion formed on the inner circumferential surface of the inner rotator which is coupled to a cam groove formed on the outer circumferential surface of the rear lens group frame, an inner guide ring for preventing rotation of the zoom ring and the rear lens group frame when the inner rotator rotates, and a driving means for rotating the inner rotator in forward and reverse directions.
Also, to achieve the above objective, there is provided a A barrel assembly of a zoom camera comprising a fixed barrel fixed to a main body of the zoom camera, a driving means installed at one side of the fixed barrel, a helicoid ring coupled to the fixed barrel by a first reciprocating means so as to be reciprocated according to the rotation of the driving means in forward and reverse directions, a guide ring coupled to the helicoid ring and linearly moved together with the helicoid ring by the first guide means along the optical axis with respect to the fixed barrel when the helicoid ring is moved back and forth, an inner helicoid ring coupled to a second reciprocating means by being inserted in the guide ring, reciprocated by a transfer force of the guide ring by the second guide means, and rotating at the same frequency as the helicoid ring, a zoom ring coupled to the inner helicoid ring by a fourth reciprocating means and where a front lens group is installed, an inner rotator coupled to the zoom ring and rotating together with the inner helicoid ring by a third guide means, a rear lens group frame, where a rear lens group is installed, coupled to the inner rotator and reciprocated by a rotational force of the inner rotator by being guided by a cam means, and an inner guide ring, supported by the guide ring, for prevent the rotation of the rear lens group frame and the zoom ring so that the zoom ring and the rear lens group frame can linearly move during the zoom operation of the front and rear lens groups.
Also, to achieve the above objective, there is provided a A barrel assembly of a zoom camera comprising a fixed barrel fixed to a main body of the zoom camera and having a first guide groove formed on the inner circumferential surface along the optical axis, a driving means installed at one side of the fixed barrel, a helicoid ring coupled to the fixed barrel by a first reciprocating means so as to be reciprocated according to the rotation of the driving means in forward and reverse directions and having a second guide groove along the optical axis, a guide ring coupled to the helicoid ring and having a first cam groove formed on the outer circumferential surface thereof and a first guide protrusion formed at one end portion thereof to be coupled to the first guide groove, the guide ring being linearly reciprocated along the optical axis with respect to the fixed barrel when the helicoid ring is rotated in forward and reverse directions, an inner helicoid ring coupled to the guide ring and a third reciprocating means and having a second guide protrusion formed on the outer circumferential surface thereof to be coupled to the second guide groove through the first cam groove, a zoom ring coupled to the inner helicoid ring by a fourth reciprocating means and where a front lens group is installed, an inner rotator coupled to the zoom ring and having a third guide protrusion formed on the outer circumferential surface thereof which is coupled to a third guide groove formed on the inner circumferential surface of the inner helicoid ring and a cam protrusion formed on the inner circumferential surface thereof, a rear lens group frame where a rear lens group is installed, and having a cam groove formed on the outer circumferential surface thereof which is coupled to the cam protrusion, and an inner guide ring, supported by the guide ring, for prevent the rotation of the rear lens group frame and the zoom ring so that the zoom ring and the rear lens group frame can linearly move along the optical axis by a rotational force of the helicoid ring.